In preparation of a battery, in order to make electrode plates better attached together to improve performance and quality of the battery, it needs to hot press a cell of the battery. Generally, for a conventional non-step type cell, it often uses a flat-plate type pressing device to hot press; but for a new step type cell, it is common to add an outer vest fixed outside the step type cell and then perform pressing, because a height of each step of the outer vest is constant, when there is a tolerance in a thickness of each step of the step type cell, it cannot ensure uniform pressure, thereby affecting the quality of the step type cell.